1. Field of the Invention
The present invention relates to a control system for an exercise machine, and more particularly to such a system which uses hydraulic means as a force to develop a resisting component which allows isodynamic resistance to be utilized by an exercise machine.
Positive work occurs during the lifting of a weight as a muscle shortens. An example of this is the common curl exercise which shortens the biceps. This shortening against resistance is called concentric contraction. Negative work occurs during the lengthening of a muscle as it limits the speed of descent of a weight. This forced lightening is called eccentric contraction.
Isotonic resistance is a constant force, produced by a compressed gas or a weight stack. Isokinetic resistance means "constant speed" resistance, but here refers to resistance such as that caused by viscous fluid being forced through an orifice. True isodynamic resistance is the combination of isokinetic and isotonic resistances. Thus isodynamic resistance could be produced by lifting a weight attached to a fluid-friction device such as a dashpot, or by lifting a weight by means of an hydraulic system having fluid friction. True isodynamic resistance always has a minimum resistance greater than zero, due to the isotonic element. The resistance varies with velocity above or below that minimum depending on whether the mode or motion is in the positive direction and thus concentric or in the negative direction and thus eccentric. Isodynamic resistance depends both on the amount of weight lifted and how fast it is lifted. Isodynamic resistance can be positive only, as long as it is greater than zero at a velocity of zero. Isodynamic resistance increases with the speed of concentric contraction while stressing the same muscle group in both the positive and negative directions of motion, unlike isokinetic exercise which stresses opposing muscle groups with concentric contractions only. Isodynamic resistance allows eccentric resistance to decrease with speed, as, when lowering a weight attached to a dashpot it is found that holding the weight stationary requires force equal to the weight, but moving the weight at its natural frictional speed of descent requires no force at all. In other words, the slower a user of an exercise machine lowers the weight, the higher the isodynamic resistance.
A user's negative strength is significantly greater than positive strength due to muscular friction. Due to the fact that muscle strength and leverage both change with position, the resistance must change automatically in order to work the muscle equally at all positions of the exercise.
Hyperplasia, or the creation of new muscle fibers by the splitting of old ones, is the most desirable ay to gain muscle strength and mass because the gains are much more permanent. Hypertrophy has been found to slow the maximum contraction rate while hyperplasia increased the maximum speed of contraction. This predomination theory suggests that a muscle is enlarged by hyperplasia at maximum exercise speeds because smaller fibers can contract faster than larger fibers. To obtain the full effect of hyperplasia, exercise must be conducted at maximum velocity. Inertia prevents maximum exercise velocities in most other exercise machines. Maximum contraction velocities are also required to insure training of all muscle fibers including the white fast twitch fibers which, along with viscosity, play a major role in the determination of a muscle's maximum contraction velocity. Slower contractions only stimulate the red slow twitch fibers. The isodynamic mode enables one to exercise at maximum intensity through the use of maximum velocity for a chosen force. This is proven by the formula P=Fv (Power equals Force times velocity). The maximum rate of contraction only regards the concentric mode of exercising. The eccentric mode occurs during the lengthening of the muscle being exercised or during the negative mode of an exercise.
The user will get the most out of the eccentric or negative mode by limiting the rate at which the resistance is let down. The exerciser reduces eccentric resistance with an increase in speed. The resistance during the concentric (positive) phase should be less than the user's strength in order to allow the lift. During the negative phase, the resistance should be greater than the user's strength in order to force him back down to the starting position. From this one can see that the negative resistance will be considerably more than the positive and therefore will cause more growth. It is important to note that the negative or eccentric resistance is very important to the growth and conditioning of muscles due to the fact that it causes more growth. Since the negative is so heavy, the chance of the user losing control is greater. If this happens and the control safety system is in effect, the resistance will immediately be reduced to zero until the user resumes the exercise in a positive direction. This safety device allows for the safety of the user and the machine.
The present invention will allow concentric resistance to increase with speed and eccentric resistance to decrease with speed. In addition, the system will allow an exercise machine to utilize gauges which illustrate the resistance for extension and flexion.
Total isolation and full range motion are very often mutually exclusive features because many muscles of the body act as what may be called "compound" or "two-joint" or "multiple-joint" muscles. That is to say that these particular muscles control both translation and rotation at a single joint or rotation at two or more joints simultaneously. This is why the single-axis rotary-form or single axis linear form movement of most machines cannot allow full-range motion. The double-headed biceps brachii is an example. The bicep is the primary muscle used in flexing or reducing the angle at the elbow. However, it has a secondary but equally important function of supporting the arm from backward rotation about the shoulder axis that is parallel to the clavicle or collarbone. Upper arm motion and forearm motion both affect the biceps' range of motion because the biceps spans both the shoulder joint and the elbow. Flexibility throughout a full range of motion can only be gained or maintained by moving the joint and muscle through their full range under resistance. Negative resistance is required to push the exerciser through a range of motion that would not be possible by stretching alone. Application of resistance through less than a full range of motion can lead to muscle development that will eventually inhibit motion beyond the range of motion of the exercises used. The control system of the present invention together with the described exerciser will enable multiple joint muscles to be trained with multiple degrees of freedom across a full range of motion at a determined ratio of torque resistance between joints to be determined both by the strength of the user and certain dimensions of the machine. Presently, swimming is the only way in which multiple-joint/double-jointed muscles may be properly trained throughout their full range of motion with a resistance present throughout said full range. The described exercise machine of the present invention will offer an alternative to swimming for such training of multiple-joint/double jointed muscles.
The ability to rain multiple joint muscles as the primary muscles with multiple degrees of freedom with all single joint muscles acting as synergists and stabilizing muscles for the multiple joint muscles would be the ideal situation. A certain ratio of torque strength exists among the different joints controlled by a multiple joint muscle due to differences in leverage at different joints which is due to different joint to tendon attachment distances. The present invention discloses a control system and an exercise machine which allow for such a training of multiple joint muscles. The present invention uses hydraulic cylinders of differing diameters attached to the various user-activated members, to respond with differing torques tot he respective muscles exerting those torques and so maintain the proper ratio of torque strength. While the ratio of torques thus remains constant (while the members are at rest--hydraulic friction varies the force while members are in motion), the overall amount of torque or force may be varied by the exercise machine control system.
A feature of the disclosed invention which is not available in any other exercise device is the utilization of true isodynamic resistance in both the positive and negative modes. Many people who exercise with isokinetic machines are lulled into exerting a force which is somewhat less than their capacity. This is because the faster the isokinetic machine is worked, the greater the required force. So, if a person is psychologically down, he will tend to exert less by exercising slower which is easily done on an isokinetic machine. This shortcoming is eliminated in the present invention by the combination of modes which sets a bottom limit to the exercise effort but allows any effort above the bottom limit to fluctuate in an isokinetic fashion. In this way the person exercising can set the isodynamic mode to something near his capacity, as this will prevent him from relaxing or working less than this setting in both the positive and negative directions. Also, most isokinetic machines have a dead band at the end of an exercise stroke. The dead band is the time (or distance) over which resistance to applied force is minimized or zero. In a fluid-friction isokinetic machine, the dead band would be caused by the compressibility of the viscous working fluid and the volumetric change of the plumbing under pressure. It corresponds to backlash in a mechanical system.
The present invention allows an exercise machine to operate in three different modes. The three modes are pos/pos, pos/neg, and reverse pos/neg. The pos/pos or double positive mode allows two opposing muscle groups to be trained concentrically and consecutively. An example of two opposing muscle groups is the biceps and triceps. The pos/neg mode is the normal exercise which most exercisers are accustomed to. The positive resistance is followed by a negative resistance after the positive resistance has been performed. The reverse pos/neg mode reverses the positive and negative resistances. For example, a leg extension exercise machine may be used as a leg extension machine in the pos/neg mode, and used as a leg curl machine in the reverse pos/neg mode. Also, an arm curl machine could be used in the pos/neg mode to perform biceps positives or contractions and then the negatives which follow. This would also be the biceps mode when lifting and lowering a weight. If the reverse pos/neg mode is used, a user would then perform triceps positives or contraction and then the subsequent negatives, as when doing pushups.
2. Description of the Prior Art
Various prior art hydraulic exercise machines and the like, as well as the apparatus and method of their construction in general, are known, and those found to be exemplary of the prior art are U.S. Pat. Nos. 4,326,707, 4,397,462, 4,681,316, 4,592,545 and 4,577,862.
U.S. Pat. No. 4,326,707 to Strecker discloses a hydraulic exerciser comprising a hydraulic control circuit, a single acting positive displacement pump, and an exercise machine designed using the control circuit and pump. The Strecker patent discloses the use of hydraulics in exercising. The Strecker patent claims to disclose isometric, isokinetic and isodynamic modes of resistance. However, the Strecker patent does not disclose a negative or eccentric force or a force greater than zero at zero velocity. Therefor, the Strecker patent does not disclose either an isodynamic mode or for that matter an isotonic mode. This is due to the fact that isodynamic resistance is a combination of isotonic and isokinetic resistance. Negative or eccentric resistance is always present when isotonic or true isodynamic resistance is present. The Strecker patent has no isotonic resistance and therefore no isodynamic resistance due to the fact that no negative or eccentric resistance is present. It is a well known fact that negative or eccentric resistance is very important to the training of muscles due to the fact that it promotes more growth than positive or concentric resistance. The Strecker patent discloses only isokinetic resistance and does not disclose isodynamic resistance. The negative or eccentric resistance present in the present invention causes it to be a substantial improvement over the Strecker patent as far as combining hydraulics and weight training is concerned. The advantages of the present invention due to the added characteristic of negative resistance may be found in numerous publications which deal with the advantages of negative resistance. The Strecker patent also fails to disclose a means of presetting different positive and negative resistances.
U.S. Pat. No. 4,465,274 to Davenport discloses a hydraulic exercise device that includes an upstanding mast whereon a number of fixed and movable exercise portions for simultaneous and sequential operation are provided, each utilizing an isokinetic load system as a load resistance against which exercises are performed although the Davenport patent wrongly claims an isotonic load system. The Davenport patent clearly discloses a hydraulic exercise machine which utilizes isokinetic resistance. The Davenport patent lacks both isotonic and true isodynamic resistance. The advantages of isodynamic resistance over isotonic resistance are stated above.
U.S. Pat. No. 4,681,316 to DeCloux discloses a hydraulic exercise machine which may be used to perform isokinetic exercise activities. The DeCloux patent lacks isotonic resistance in both the positive and negative directions. Therefore, the DeCloux patent lacks isodynamic and isotonic resistance. The advantages of isodynamic resistance over isokinetic resistance are stated within the prior art which discusses isodynamic resistance.
The prior art searched was void of disclosures of exercise machines with displaceable members which allow a user to train multiple joint muscles throughout their full range of motion. Therefore, the prior art was also void of any system or exercise machine which would enable a person to train multiple-joint muscles throughout their full range of motion while utilizing isodynamic resistance.
The prior art is also void of a system which allows for one value of concentric resistance and another value of eccentric resistance to be preset.
These patents or known prior art disclose various implementations of hydraulic methods which may be used to develop isokinetic resistance. However, it is believed that the present invention is unique in the development of true isodynamic resistance using fluid and weight means, which has an ability to produce resistance with inertia which is important for the development of peak forces leading to peak strength production.